Due to the high school's staggered schedule, Severin's class graduated in January 1948, rather than in mid-year as typical.

[8] Severin grew up in an artistic household where her father, a World War I veteran, eventually became a designer for the fashion company Elizabeth Arden during the 1930s.

[13] In her teens, Severin took what she recalled as "a couple of months" of cartooning and illustration classes, and attended Pratt Institute in Brooklyn "for one day and said, 'This is a college', and I wanted to draw and make money".

[13] Her first job was doing clerical work for an insurance company in downtown Manhattan "for a couple of years" while still living at home.

[13] Marie Severin's earliest recorded comic-book work is coloring EC Comics' A Moon, a Girl ...

'"[17] Severin repeatedly refuted that assertion, which became part of comics lore,[18] while also saying she sometimes used coloring to "kind of shield" some gruesome content, noting, I would never assume an editorial position.

With Lee, Severin co-created the fictional cosmic entity the Living Tribunal in Strange Tales #157 (June 1967).

[22] A panel illustrated by Severin for a July 1967 issue that featured both characters was later incorporated into the cover art of Pink Floyd’s sophomore album, A Saucerful of Secrets, released the next year.

[23] Severin was Marvel's head colorist until 1972, at which point she turned most of her coloring duties over to George Roussos so that she could do more penciling assignments.

She drew stories of the Sub-Mariner and the Hulk, and the covers or interiors of titles including Iron Man, Conan the Barbarian, Kull the Conqueror,[25] The Cat,[26] and Daredevil.

[33] During the following decade, Severin penciled the "Impossible Tale" of the "Li'l Soulsearchers" in issue #31 (Aug. 1998) of Claypool Comics' superhero-humor comic Soulsearchers and Company, inked by fellow Silver Age veteran Jim Mooney; and she inked Dave Cockrum's penciling in issue #43 (July 2000).

[citation needed] Severin spoke at a 1974 New York Comic Art Convention panel on the role of women in comics, alongside Flo Steinberg, Jean Thomas (sometime-collaborator with then-husband Roy Thomas), Linda Fite (writer of The Claws of the Cat) and fan representative Irene Vartanoff.

[42] In consideration of her contributions to comics, ComicsAlliance listed Severin as one of twelve women cartoonists deserving of lifetime achievement recognition.

[45] Severin was also inducted into the Harvey Awards Hall of Fame alongside her brother John, and fellow Mad contributors Will Elder, Jack Davis, and Ben Oda.